Gruyère-Spinach Potatoes Au Gratin Recipe

This Gruyère-Spinach Potatoes Au Gratin Recipe is well worth every minute it takes to prepare. The flavors are deep, the textures are smooth, and the overall takeaway is one of over-the-top, comforting deliciousness! A potato gratin with spinach never disappoints!Talk about vegetarian comfort food! Oh my!

And you know what’s amazing about this? It’s full of potatoes and delicious creaminess, but it isn’t too rich or heavy.

It is however, delicious, packed with flavor, and super satisfying!

I love the layering process involved in creating this incredible gratin. It definitely feels a bit like an art project when I make this — both in flavor and in design.

What are Potatoes Au Gratin?

When something is cooked au gratin (or gratin), it generally means to give a dish a golden brown top.

People often think for a dish to be au gratin, it should be topped with breadcrumbs and/or grated cheese, and it’s those ingredients that become golden brown. Sure with these ingredients, a dish can certainly be au gratin — however, it doesn’t need these toppings to be considered au gratin.

So what exactly are Potatoes Au Gratin? In the case of this recipe, they’re a delectable mixture of cream, herbs and spices, coating sliced potatoes, topped with grated onion and Gruyère, and beautifully browned in the oven.

The word gratin, also refers to an oval shaped baking dish — which is the way you’ll typically see most au gratins presented. Though mine is rectangle. 🙂

I’ve laid out the steps for assembly very carefully for you because much of the success of this Gruyère-Spinach Potatoes Au Gratin is in the the layering process.

Here’s a sneak peak . . . .

Two layers of potato slices that have been soaking the the cream-spice-herb mixture.

The potatoes are then topped with grated onion and Gruyère.

Now piles of fresh spinach.

Then these three steps are repeated and followed by more potatoes, onions and cheese. It will literally be almost overflowing.

So . . . . we weigh it down for about an hour with another pan and heavy cans, compacting all of the ingredients together.

There are a couple of more quick steps after this and then it’s off to the oven.

Yes, this recipe takes time, and honestly, if you don’t love cooking, it might not be one you want to try. If you really enjoy the cooking process and being in the kitchen, this for you.

Either way though, it’s super delicious and you might not want to miss out!

This is a recipe where it’s important to read through all the steps before you get started.

The thinner you slice the potatoes, the better. If they’re super thin, they become almost like flat pasta, and the Gruyère links it all together.

Peel the onion and cut it in half or quarters to grate it. A food processor with the grater attachment is easiest. Alternately, you can slice the onion super thinly. Add the grated onion to a strainer over a bowl and set aside.

In a large sauce pot, combine the half and half with the garlic, thyme, nutmeg and allspice. Bring to a boil and then immediately reduce to a low simmer. Simmer until the the mixture has reduced by about 1/4, about 25 minutes. Remove from the stove, strain, and add the salt and pepper. Let it cool until it's warm, or to room temperature.

Peel the potatoes and slice them as thinly as possible, adding them to the half and half mixture as you go. Make sure the slices aren't stuck together and that all of them become well coated with the mixture. (I use the slicer attachment on my food processor for this.) Let the potato slices soak for about 30 minutes.

Assembly

Brush a bit of the melted butter on the bottom and sides of an approximately 9 X 13 X 2-inch baking dish.

Without wiping them off, add two even layers of the potato slices from the half and half mixture. You should not be able to see the bottom of the dish when you're done. Sprinkle lightly with salt and pepper. DO NOT THROW OUT THE HALF & HALF MIXTURE!

Squeeze any remaining liquid out of the onions and sprinkle about 1/3 of them evenly on the potatoes.

Now sprinkle 1 cup of the Gruyère cheese on the onions.

Add 1/2 of the spinach leaves -- they will not lay flat.

Repeat steps 2 through 5.

Add another two layers of the potatoes. Do not worry if nothing is laying flat -- at this point, it will look too high and rounded, coming above the edges of the dish in the center. This is how it should be. Set aside the remaining melted butter, onions, cheese, and all of the half and half mixture.

Cover the dish tightly with plastic wrap and put a second dish directly on top -- ideally one that's the same size so the bottom of the top dish is pressing directly onto the plastic-covered, top layer of potatoes. Everything will flatten out at this point. Now weigh down the top dish -- canned food is perfect. Fill the top pan with as many cans as will fit, and place this entire set-up in the refrigerator for 1 hour. (This is how we drain any excess moisture.)

Preheat the oven to 375°F, remove from the refrigerator and take off the weights and top dish. Keeping it covered with the plastic, holding it over the sink, slowly pour out any excess liquid from one of the corners. You can hold the palm of one hand down of the top surface of the gratin (on the plastic), to be sure nothing slides around.

Remove the plastic wrap completely and sprinkle the top with a bit more salt and pepper, and then the remaining onions and cheese.

Stir the saved half and half mixture to ensure the garlic and herbs are not sitting at the bottom. Pour it into the gratin until it goes about 3/4 the way up the sides (it will be about 1 1/2 cups or so). Use a dull knife to move the potatoes a tiny bit along the edges, to be sure it seeps through to the bottom.

Drizzle the top with the remaining melted butter, place the pan on a baking sheet and then it in the preheated 375°F oven. Bake for 50 minutes. Then cover the pan loosely with foil and continue to bake for another 25 minutes.

If the top of the gratin hasn't become golden brown, place it under the broiler briefly, about 30 seconds. Let the gratin sit for at least 45 minutes before cutting and serving.

Recipe Notes

This is a dish that only gets better with time. You can make the entire thing up to 3 days ahead of time and reheat it, covered, in a 375°F oven for about 30 minutes.

I made something very similar only difference is i add artichoke hearts and ricotta cheese – kind of tastes like spinach artichoke dip which my husband adores so i made up this dish to give him the taste of artichoke dip in a heartier more filling way.

Oh Angie, the addition of artichoke hearts and ricotta sounds amazing! Do you use frozen artichoke hearts? If so, how much and do you adjust the cooking time? Also wondering the amount of ricotta and if necessary to adjust cooking time. Thanks so much!

Hi Linda — in case Angie doesn’t respond . . .
I’d say you could use frozen artichokes, if you thaw them completely first.Though, I think marinated artichoke hearts, drained, would be even better though. I’d cut them into fourths, removing any tough leaves, and use about 2 cups — 1 cup evenly distributed under each layer of cheese. For the ricotta, I’d spread about 3/4 cup per cheese layer, and remove about 1/2 cup of the Gruyere from each. I’d also suggest mixing the full amount of ricotta first with 1 egg and seasoning it well with salt and pepper. I haven’t done this before, but I think these amounts will probably work. Best of luck and please let me know how it goes if you give it a try. 🙂

Potato Au Gratin is seriously one of my favorite side dishes of all times. In fact, I’ve just made it for my daughter’s birthday last Saturday. I’ve never thought of adding spinach to it. Great idea! Gotta try it next time!